#!/usr/bin/perl

#  This test Perl program checks out all the different ways I could think of,
#  of what one gets when in scalar context versus list context.

#  1) A real list:

undef $myscalar;
undef @mylist;
@real_list = ("s1","s2");
$myscalar = @real_list;
@mylist   = @real_list;

print "Case 1)  Using a real list:\n";
print "       \@real_list = (\"s1\",\"s2\");\n";
print "       \$myscalar = \@real_list;      yields ",(defined $myscalar)?$myscalar:"UNDEFINED","\n";
print "   and \@mylist   = \@real_list;      yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<\n";
print "                                           =>"  ,(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n";
print "                                       and =>"  ,(defined $mylist[2])?$mylist[2]:"UNDEFINED","<\n\n";



#  2) Putting ("s1","s2") on the right hand side of an assignment:

undef $myscalar;
undef @mylist;
$myscalar = ("s1","s2");
@mylist   = ("s1","s2");

print "Case 2) Using a supplied list:\n";
print "       \$myscalar = (\"s1\",\"s2\");     yields $myscalar      (!!)  Note parenthesis in scalar context.\n";
print "   and \@mylist   = (\"s1\",\"s2\");     yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<\n";
print "                                           =>"  ,(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n";
print "                                       and =>"  ,(defined $mylist[2])?$mylist[2]:"UNDEFINED","<\n\n";



#  3-A) Using Backticks on a Command That Returns Something:

undef $myscalar;
undef @mylist;
$myscalar = `lsvg rootvg`;
@mylist   = `lsvg rootvg`;

print "Case 3-A) Using backticks on a Command That Returns Something:\n";
$myscalar =~ s/\n/<CR>\n/g;
$myscalar =~ s/<CR>\n$/<CR>/g;
print "       \$myscalar = \`lsvg rootvg\';   yields one large, 10-line string\n>$myscalar<\n\n";
print "   and \@mylist   = \`lsvg rootvg\';   yields a 10-element list,\n";
$mylist[0] =~ s/\n$/<CR>/;
print "\$mylist\[ 0\] =>$mylist[0]<\n";
$mylist[1] =~ s/\n$/<CR>/;
print "\$mylist\[ 1\] =>$mylist[1]<\n";
$mylist[2] =~ s/\n$/<CR>/;
print "\$mylist\[ 2\] =>$mylist[2]<\n";
print "                  ...\n";
$mylist[9] =~ s/\n$/<CR>/;
print "\$mylist\[ 9\] =>$mylist[9]<\n";
print "\$mylist\[10\] =>"  ,(defined $mylist[10])?$mylist[10]:"UNDEFINED","<\n\n";



#  3-B) Using Backticks on a Command That Returns Nothing:

undef $myscalar;
undef @mylist;
print "1\n";
$myscalar = `lsvg rootvg >/dev/null`;
print "2\n";
@mylist   = `lsvg rootvg >/dev/null`;

print "3\n";
print "Case 3-B) Using backticks on a Command That Returns Nothing:\n";
print "4\n";
$myscalar =~ s/\n/<CR>\n/g;
print "5\n";
$myscalar =~ s/<CR>\n$/<CR>/g;
print "6\n";
print "       \$myscalar = \`lsvg rootvg \>/dev/null\`;   yields >",(defined $myscalar)?$myscalar:"UNDEFINED","<        (!!) #  Note null in scalar context\n";
print "7\n";
print "   and \@mylist   = \`lsvg rootvg \>/dev/null\`;   yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<   #  but undefined in list context.\n";
print "                                                      =>"  ,(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n\n";



#  4) Using a Successful Pattern Match:

undef $myscalar;
undef @mylist;
$myscalar = "abc" =~ /a/;
@mylist   = "abc" =~ /a/;

print "Case 4) Using a Successful Pattern Match:\n";
print "       \$myscalar = \"abc\" =~ /a/;    yields $myscalar\n";
print "   and \@mylist   = \"abc\" =~ /a/;    yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<\n";
print "                                            >"  ,(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n\n";



#  5) Using an Unsuccessful Pattern Match:

undef $myscalar;
undef @mylist;
$mylist[0] = "mytest0";      #  This proves that these mylist elements
$mylist[1] = "mytest1";      #  actually get undefined, not merely not set.
$myscalar = "abc" =~ /z/;
@mylist   = "abc" =~ /z/;

print "Case 5) Using an Unsuccessful Pattern Match:\n";
print "       \$myscalar = \"abc\" =~ /z/;    yields =>",(defined $myscalar)?$myscalar:"UNDEFINED","<              (!!) #  Note null in scalar context,\n";
print "   and \@mylist   = \"abc\" =~ /z/;    yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<          #  but undefined in list context.\n";
print "                                           =>",(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n\n";



#  6-A) Using a Successful Pattern Match on a Backtick'd Command That Returns Something:

undef $myscalar;
undef @mylist;
$myscalar = `lsvg rootvg` =~ /PP/;
@mylist   = `lsvg rootvg` =~ /PP/;

print "Case 6-A) Using a Successful Pattern Match on a Backtick'd Command That Returns Something:\n";
print "       \$myscalar = \`lsvg rootvg\` =~ /PP/;    yields =>$myscalar<\n";
print "   and \@mylist   = \`lsvg rootvg\` =~ /PP/;    yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<\n";
print "                                                    =>",(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n\n";



#  6-B) Using a Successful Pattern Match on a Backtick'd Command That Returns Nothing:

undef $myscalar;
undef @mylist;
$myscalar = `lsvg rootvg >/dev/null` =~ /PP/;
@mylist   = `lsvg rootvg >/dev/null` =~ /PP/;

print "Case 6-B) Using a Successful Pattern Match on a Backtick'd Command That Returns Nothing:\n";
print "       \$myscalar = \`lsvg rootvg >/dev/null\` =~ /PP/;    yields =>$myscalar<\n";
print "   and \@mylist   = \`lsvg rootvg >/dev/null\` =~ /PP/;    yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<\n";
print "                                                               =>",(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n\n";



#  7) Using an Unsuccessful Pattern Match on a Backtick'd Command:

undef $myscalar;
undef @mylist;
$mylist[0] = "mytest0";      #  This proves that these mylist elements
$mylist[1] = "mytest1";      #  actually get undefined, not merely not set.
$myscalar = `lsvg rootvg` =~ /zz/;
@mylist   = `lsvg rootvg` =~ /zz/;

print "Case 7) Using an Unsuccessful Pattern Match on a Backtick'd Command:\n";
print "       \$myscalar = \`lsvg rootvg\` =~ /zz/;    yields =>",(defined $myscalar)?$myscalar:"UNDEFINED","<        (!!) #  Note null in scalar context,\n";
print "   and \@mylist   = \`lsvg rootvg\` =~ /zz/;    yields =>",(defined $mylist[0])?$mylist[0]:"UNDEFINED","<    #  but undefined in list context.\n";
print "                                                    =>",(defined $mylist[1])?$mylist[1]:"UNDEFINED","<\n\n";