use strict;
use warnings;

my $str = '<start> </begin> </this> </that> <begin> </start>';

counttags ($str, 'begin');

sub counttags {
    my ($test, $target) = @_;
    my $stag = $test =~ /<$target>/g;
    my $etag = $test =~ /<\/$target>/g;
    if($stag != $etag) {
        print "Number of Start and End tags for element $target does not match";
    }
}

##</code><code>##

Number of Start and End tags for element begin does not match