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Re^6: Turning on regexp debugging at runtime

by roboticus (Chancellor)
on Sep 24, 2014 at 20:28 UTC ( #1101864=note: print w/replies, xml ) Need Help??


in reply to Re^5: Turning on regexp debugging at runtime
in thread Turning on regexp debugging at runtime

SBECK:

In that case, go ahead and recompile the regex in the debugger, like this:

do { use re qw(Debug More); $re1=qr/g/; }

We simply create a block and inside it, we turn on regex debug mode, and compile the regex.

Here's the test run I did:

$ cat t.pl use strict; use warnings; my $re1 = qr/p/; my $re2 = qr/t/; use re qw(Debug More); my @list = ('alpha', 'beta', 'gamma', 'delta'); for (@list) { print $_, "\n"; if (/$re1/) { print "has P\n" } if (/$re2/) { print "has T\n" } } $ perl -d t.pl <<< snip >>> main::(t.pl:4): my $re1 = qr/p/; DB<1> s main::(t.pl:5): my $re2 = qr/t/; DB<1> main::(t.pl:9): my @list = ('alpha', 'beta', 'gamma', 'delta'); DB<1> main::(t.pl:11): for (@list) { DB<1> main::(t.pl:12): print $_, "\n"; DB<1> alpha main::(t.pl:13): if (/$re1/) { print "has P\n" } DB<1> main::(t.pl:13): if (/$re1/) { print "has P\n" } DB<1> has P main::(t.pl:14): if (/$re2/) { print "has T\n" } DB<1> p { use re qw(Debug More); $re1=qr/g/; } Compiling REx "g" Final program: 1: EXACT <g> (3) 3: END (0) anchored "g" at 0 (checking anchored isall) minlen 1 DB<2> s main::(t.pl:12): print $_, "\n"; DB<2> beta main::(t.pl:13): if (/$re1/) { print "has P\n" } DB<2> Guessing start of match in sv for REx "g" against "beta" Did not find anchored substr "g"... Match rejected by optimizer main::(t.pl:14): if (/$re2/) { print "has T\n" } DB<2> main::(t.pl:14): if (/$re2/) { print "has T\n" } DB<2> has T main::(t.pl:12): print $_, "\n"; DB<2>

If you want to switch back and forth, then you may want another variable that you can use to hold the original (nondebug) version, so you can copy it back after you're done with the debug version.

Note: As you can see, I originally intended to leave regex debugging on by doing so after compiling all the regexes. But it seems that it was optimized out, so that's why I had to wrap it during debugging. It may be easy to leave the regex engine in debug mode so you can avoid the do { } block, but once I had something that worked, I stopped.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

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