/^/m|/$/m||B|$&|$`|$'|变量捕获|()?|(?:pattern)|(?<LABEL>PATTERN)|$+{LABEL}|(|)|g{LABEL}

#!/usr/bin/perl

use strict;
use warnings;

$_='

 $$   oinn     &&&
ninq   kdownc
aninp
    kkkk';

if (/(.*)k/){print "$1
";}else{print "no match
";}

#   kkk

if (/^n(.*)/m){print "$1
";}else{print "no match
";}

#inq   kdownc

if (/(.*n.n.*)/){print "$1
";}else{print "no match
";}

#no match

if (/.*(Bn.nB).*/){print "$& and $1
";}else{print "no match
";}

#aninp and nin

if (/w*(i)w*/){print "$& and $1 and $` and $'
";}else{print "no match
";}

#oinn and i and
#
# $$    and      &&&


my $new_words = 
'sewfbiurev214`7i074o//m,m][g
sw  d
       trp';

if ($new_words =~ /(.*)g$/m){print "$1
";}else{print "no match
";}

#sewfbiurev214`7i074o//m,m][

my $test = (<> =~ /^sd(.*)/m );if ($test){print "right!,it is $1
";}else{print "no match
";}

#sdkkk
#right!,it is kkk

my $what = shift @ARGV;if ($new_words =~ /(.*)($what$)/m){print "right!,it is $1 and $2
";}else{print "no match
";}

# perl test.pl g
# right!,it is sewfbiurev214`7i074o//m,m][ and g

$new_words =~ /(.*)g$/m;$new_words =~ /(.*)s$/m;print "$1
";

#sewfbiurev214`7i074o//m,m][

$new_words =~ /(.*q)?(.*)g$/m;print "$2
";

#sewfbiurev214`7i074o//m,m][

$new_words =~ /(?:.*q)?(.*)g$/m;print "$1
";

#sewfbiurev214`7i074o//m,m][

$new_words =~ /(?:.*q)?(2|s)(.*)g$/m;print "$1 and $2
";

#s and ewfbiurev214`7i074o//m,m][

$new_words =~ /(?:.*q)?(?:2|s)(?<label>.*)g$/m;print "$+{label}
";

#ewfbiurev214`7i074o//m,m][

$new_words =~ /(?:.*q)?(?<label2>(2|s))(?<label>.*)g$/m;print "$+{label} and $+{label2}
";

#ewfbiurev214`7i074o//m,m][ and s

my $test2 = 'aavvbbssd';
$test2 =~ /^(?<word1>.)g{word1}(?<word2>.)g{word2}/m;print "$+{word2} and $+{word1}
";

#v and a

print "|$`<$&>$'|
";

#|<aavv>bbssd|