10-25-2008
Quote:
Originally Posted by
nwboy74
You're not going to be able to use a single regular expression to accomplish that. You might try something like:
if ($str !~ /([a-z]).*\1/ && $str =~ /^[a-z]+$/) {
...
}
I agree, a single regexp would be too complicated, but I think you also just did his school/course work for him.
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re(3pm) Perl Programmers Reference Guide re(3pm)
NAME
re - Perl pragma to alter regular expression behaviour
SYNOPSIS
use re 'taint';
($x) = ($^X =~ /^(.*)$/s); # $x is tainted here
$pat = '(?{ $foo = 1 })';
use re 'eval';
/foo${pat}bar/; # won't fail (when not under -T switch)
{
no re 'taint'; # the default
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no re 'eval'; # the default
/foo${pat}bar/; # disallowed (with or without -T switch)
}
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# compile and run time
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(We use $^X in these examples because it's tainted by default.)
DESCRIPTION
When "use re 'taint'" is in effect, and a tainted string is the target of a regex, the regex memories (or values returned by the m// opera-
tor in list context) are tainted. This feature is useful when regex operations on tainted data aren't meant to extract safe substrings,
but to perform other transformations.
When "use re 'eval'" is in effect, a regex is allowed to contain "(?{ ... })" zero-width assertions even if regular expression contains
variable interpolation. That is normally disallowed, since it is a potential security risk. Note that this pragma is ignored when the
regular expression is obtained from tainted data, i.e. evaluation is always disallowed with tainted regular expresssions. See "(?{ code
})" in perlre.
For the purpose of this pragma, interpolation of precompiled regular expressions (i.e., the result of "qr//") is not considered variable
interpolation. Thus:
/foo${pat}bar/
is allowed if $pat is a precompiled regular expression, even if $pat contains "(?{ ... })" assertions.
When "use re 'debug'" is in effect, perl emits debugging messages when compiling and using regular expressions. The output is the same as
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ity of the match. Using "debugcolor" instead of "debug" enables a form of output that can be used to get a colorful display on terminals
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strings on/off, pre-point part on/off. See "Debugging regular expressions" in perldebug for additional info.
The directive "use re 'debug'" is not lexically scoped, as the other directives are. It has both compile-time and run-time effects.
See "Pragmatic Modules" in perlmodlib.
perl v5.8.0 2002-06-01 re(3pm)