deleting characters from a string but the characters are in a variable

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

hi
i want to remove some characters from a string but the characters are in a variable wich may have its value from a GUI TextBox, my program is:

use strict;
use warnings;
my $string = "aabbzzb";
my $oldchars = "ab";
my $newchars = "xx";
$_ = $string;
#replace the chars by "x" char.
eval "tr/$oldchars/$newchars/, 1" or die $@;
$string = $_;
#then delete the 'x' char.
$string =~ tr/x//d;
print $string; #will print zz
[download]

can you suggest a best methods!.
thanks

Comment on deleting characters from a string but the characters are in a variable Download Code

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Re: deleting characters from a string but the characters are in a variable by moritz (Cardinal) on Nov 12, 2008 at 11:07 UTC
If you just want to delete them: `$string =~ s/[$oldchars]//g` [download] If you want to replace them: `eval "\$string =~ tr/$oldchars/$newchars/"` [download] In both cases you might need to escape something if there are meta characters, for example with quotemeta for the regex.	[reply] [d/l] [select]
Re: deleting characters from a string but the characters are in a variable by GrandFather (Saint) on Nov 12, 2008 at 11:07 UTC
Well, you can simplify the translate to a single line: use strict; use warnings; my $string = "aabbzzb"; my $oldchars = "//; print `dir .`; \\\$string =~ tr/"; eval "\$string =~ tr/$oldchars//d"; print $string; #will print zz [download] but as you may notice from the sample $oldChars string a savy user could take advantage of the string eval to do interesting stuff. Probably you would be better to use a regex: `$string =~ s/[$oldchars]//g;` [download] which at least is a little harder to subvert. Better still would be to sanitise $oldchars before it is used in the regex, but how you do that depends a great deal on what is appropriate in oldChars. Perl reduces RSI - it saves typing	[reply] [d/l] [select]
Re: deleting characters from a string but the characters are in a variable by Anonymous Monk on Nov 12, 2008 at 10:59 UTC
You don't need to use eval/tr, just use s///	[reply]
Re: deleting characters from a string but the characters are in a variable by ww (Archbishop) on Nov 12, 2008 at 12:19 UTC
Is your question re an appropriate method of deleting "some characters" or re getting those chars "from a GUI TextBox" to your script?	[reply]
Re^2: deleting characters from a string but the characters are in a variable by Anonymous Monk on Nov 12, 2008 at 13:38 UTC
it is about an appropriate method of deleting "some characters" referenced to by a variable, the presented answers are excellent thanks for all	[reply]