Re^3: Regular expression match and substitution

It's not a good idea because it's too easy to inject code. Even if the current user of the code wouldn't do so, it might eventually make its way to where an untrusted user supplies the data. A parser is the easiest way to make sure the input is safe.

You're getting "Use of uninitialized value" error because you didn't give any value to $sym{'$b'}.

yes, eval works on strings:

$expr = '$x + 1';
print("$expr = ");
$expr =~ s/(\$\w+)/\$sym{'$1'}/g;
$sym{'$x'} = 3;
$val = eval $expr;
die("Bad equation: $@$/") if $@;
print("$val$/");
[download]

But please don't do that!

Comment on Re^3: Regular expression match and substitution Download Code

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Re^4: Regular expression match and substitution by pip9ball (Acolyte) on Nov 09, 2004 at 19:42 UTC
$sym{'$b'} is already defined. `my $p = "$sym{'$b'}/helloworld/test.dat"; $sym{'$b'} = "my"; my $val = eval $p; print "p = $val\n";` [download] This doesn't work as it should. -P	[reply] [d/l]
Re^5: Regular expression match and substitution by ikegami (Patriarch) on Nov 09, 2004 at 21:35 UTC
For starters, `my/helloworld/test.dat` is not valid Perl. (bare word my divided by bare word helloworld divided by bare word test concatenated with bare word dat?) So add quotes. Two, you want the $vars to be in $p instead of being interpolated, so use single quotes or escape the $ (and any @) in the literal. `my $p = "\"\$sym{'\$b'}/helloworld/test.dat\""; # my $p = 'qq[$sym{'$b'}/helloworld/test.dat]'; # alternative # my $p = '"$sym{\'$b\'}/helloworld/test.dat"'; # alternative # my $p = q["$sym{'$b'}/helloworld/test.dat"]; # alternative $sym{'$b'} = "my"; my $val = eval $p; print "p = $val\n";` [download]	[reply] [d/l] [select]