Just remember \W will not include _ (the underscore) it's part of \w world. To get the "real" alphabet and be nice to locales, try using the posix class [:alpha:] like so:

#!/usr/bin/perl

$alpha = 'aeiou_XZY_^#@_123_BCD';

($one = $alpha) =~ s/\W//g; # _ stays
($two = $alpha) =~ s/[^[:alpha:]]//g; # _ gone

print $one, "\n";
print $two, "\n";
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-derby