I don't know why you want a regex for that, but here you go: 
use strict;
use warnings;

my $str = "hello\nworld";
my ($first, $last);

$str =~ m/ (?{ $first = substr($str, 0, 1); $last = substr($str, -1) }
+) /x;
print "first: '$first';    last: '$last'\n";

[download]

However note the caveats of (?{ ... }) groups as documented in perlre.

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In reply to Re: regex for string by moritz
in thread regex for string by saranperl

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