perl modifier(e)

#Method 1:
use strict;

my $string = "Nikil";

$string =~ s/^([A-Za-z]+)/length($1)/e;

print $string, "\n";


#Method 2:
use strict;

my $string = "Nikil";

$string =~ s/([Ss][A-Za-z]*)/'<'.uc($1).'>'/e;

print $string, "\n";