$hash =~ s/[^a-zA-Z0-9]//g;
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ITYM $hash =~ y/a-zA-Z0-9//cd; HTH. HAND.

$ perl -MBenchmark=cmpthese -le 'cmpthese( 500_000, { s => sub { $_ = 
+q{123#$%abc^&*DEF}; s/[^a-zA-Z0-9]//g }, y => sub { $_ = q{123#$%abc^
+&*DEF}; y/a-zA-Z0-9//cd; } } )'
      Rate    s    y
s 174825/s   -- -80%
y 862069/s 393%   --
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