$string =~ tr/A-Za-z0-9.-_//cd;
You forgot to escape the hyphen, the one you want taken literally: 
$string =~ tr/A-Za-z0-9.\-_//cd;

[download]

Yours will keep everything in the range 

./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_

[download]
too, which is more than you wanted.

In reply to Re^2: regex question by bart
in thread regex question by Anonymous Monk

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