Re^3: How to use a variable in tr///

[merlyn]

why not just eval?

Because with eval, you must worry about delimiters. For example, if either string had contained "/", the eval example given elsewhere in this thread would fail. Also, eval invites disaster in a proxy-privilege environment (like CGI or other daemons).

The lookup table isn't hard to create:

## initialization
my $old = 'abc';
my $new = 'xyz';
my %table; @table{split //, $old} = split //, $new;
my $table_re = join '|', map quotemeta reverse sort keys %table;

## the deed
my $string = 'abracadabra';
$string =~ s/($table_re)/$table{$1}/g;

[Roy Johnson]

The "why not just eval?" referred to the case of embedding an eval'd tr/// in an s///e, which would be no better. But your cautions are valid. [Update: and addressed here]

Update:
Though for character replacement, I'd build the regex using a character class rather than alternation:

my $table_re = sprintf '[%s]', join '', map quotemeta, keys %table;