You have a string, probably code and want to find an unused character to use as a delimiter for a quote-ish operator.

For me this arose using Filter::Simple on arbitrary code.

The snippet uses tr/// backwards in a sense, the eval is required as tr's char sets are determined at compile time

TIMTOWTDI but it think this is nice, though perhaps not best. 

$possibly_safe = "^!|~¦¡£\0";
$mystery_str = '$a !~ /qr^some|thing^';
$mystery_str =~ tr!/!!d; # make eval interpolation safe
eval "(\$safe = \$possibly_safe) =~ tr/$mystery_str//d";
print $safe; # "¦¡£\0"

[download]
Update: There's a bit of chicken-egg action here. Can't believe I didn't notice it for 6 months.
Oh, the shame.

The old code: 

$possibly_safe = "^!|~¦¡£\0";
$mystery_str = '$a !~ qr^some|thing^';
eval "(\$safe = \$possibly_safe) =~ tr/$mystery_str//d";
print $safe; # "¦¡£\0"

[download]

In reply to Finding a safe char with tr///d by bsb

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