Re: the only difference is the 'x' after '/g'

tom arnall am Freitag, 31. März 2006 09.56:
i need the blank in 'From [' etc in order to distinguish it from the
strings with 'From:' one solution to the problem, btw, is to use '\s'
instead of a literal blank. does this behavior rank as a bug in perl?

No, absolutely not.

To make your distiction, you *have* to use the \s with the /x modifier;
without, you can use either.

The /x modifier's aim is to allow readable *formatting* of complex regexes
with spaces, line brakes, comments (#). ' ' in this case is irrelevant for
the matching. Look at the beginning of

perldoc perlre

hth!

Hans

[bottom post order:]
On Thursday 30 March 2006 05:15 am, Hans Meier (John Doe) wrote:
tom arnall am Donnerstag, 30. März 2006 12.36:
the following code:

my (@main);
$_="
From a
From: b
From: c
From: d
";
@main = /From [^\n]*?\n.*?(From: .*?\n).*?/gx;
print "@main";
print "------------------------------\n";
@main = /From [^\n]*?\n.*?(From: .*?\n).*?/g;
print "@main";

produces:

From: b
From: d
------------------------------
From: b

the only difference between the two regex lines is the 'x' after '/g'
in the first of the two regex lines.

indeed :-)

And your question could be: Why does this produce different results?

There's an additional difference on the semantic level: spaces in the 1st
regex are irrelevant. Look at the first regex space: in the 2nd regex, it
matches (only) in "From a", but not in "From: c", whereas the 1st regex
matches "From a" *and* "From: c".

/From[^\n]*?\n.*?(From: .*?\n).*?/gx;
and
/From[^\n]*?\n.*?(From: .*?\n).*?/g;
produce both the same output.

hth!
Hans
.

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