Be sure to note that it doesn't work for substitutions:

sub  prematch (;$) { substr((@_ ? $_[0] : $_), 0, $-[0]) }
sub     match (;$) { substr((@_ ? $_[0] : $_), $-[0], $+[0] - $-[0]) }
sub postmatch (;$) { substr((@_ ? $_[0] : $_), $+[0]) }

my $foo = 'Hello, world!';
$foo =~ s/l+/r/;

print "prematch(",prematch($foo),")\n";
print "match(",match($foo),")\n";
print "postmatch(",postmatch($foo),")\n";
print "`(",$`,")\n";
print "&(",$&,")\n";
print "'(",$',")\n";
[download]

produces

prematch(He)
match(ro)
postmatch(, world!)
`(He)
&(ll)
'(o, world!)
[download]

        - tye (but my friends call me "Tye")