in reply to Regexp dashes at boundaries

Your regular expression doesn't do what you think it does (I think!). The alternation meta-character | works on the two entities directly next to it. You need to use parentheses with your alternation, maybe like this: 
$text =~ s/(\bArmy\b)|(U\.S\. Army)/US-Army/g;

[download]
 Update: Arghh! Completely disregard. Alternation extends further than I said unless you limit it with parentheses. I seem to be living in opposite land today.

... but it is cleaner to "factor out" the "Army" string and do something similar to: 
$text =~ s/(U\.S\.)?\bArmy/US-Army/g;

[download]
Note: completely untested!

Hope this helps.

Replies are listed 'Best First'.
Re^2: Regexp dashes at boundaries
by tlm (Prior) on Mar 17, 2005 at 23:22 UTC

    The alternation meta-character | works on the two entities directly next to it.

    Not in Perl: 

    $t = 'abcd';
$t =~ s/bc|xy/pq/;
print "$t\n";

==> apqd

    [download]
    If what you said were true, the match above would have failed, and the contents of $t would have remained unchanged.

    the lowliest monk

[reply]
[d/l]
[select]
      and for possible further illumination: 
      $t = 'abcd';
$t1 = 'ababxycdcd';
$t2 = 'ababxycdcd';
$t3 = 'ababxycdcd';     # same as $t2, which is identical to $t1
$t4 = 'ababxycdcd';     # still the same...

$t =~ s/bc|xy/pq/;
print "\$t is: $t\n";

$t1 =~ s/(ab|xy)/pq/;
print "\$t1 is: $t1\n";

$t2 =~ s/(ab|xy)/pq/g;
print "\$t2 is: $t2\n";

$t3 =~ s/(ab)|(xy)/pq/g;
print "\$t3 is: $t3\n";

$t4 =~ s/((ab)|(xy))/pq\1/g;  #capture regex -outer (); grouping () in
+side
print "\$t4 is: $t4\n";

=head1 OUT
Output of C:\_perl\pl_test>perl 440581.pl
$t is: apqd             matched the 'b'
$t1 is: pqabxycdcd      parenthesdized the alt; now matches the FIRST 
+'ab'
$t2 is: pqpqpqcdcd      added /g (match globally) replaces both 'ab's 
+and the xy
$t3 is: pqpqpqcdcd      Shifting parens ==> no change, here
$t4 is: pqabpqabpqxycdcd  Capturing regex -- 3 'pq' pairs, each pair f
+ol by 'ab' or 'xy'
=cut

      [download]
      additional example added
[reply]
[d/l]
Re^2: Regexp dashes at boundaries
by cormanaz (Deacon) on Mar 17, 2005 at 22:33 UTC
    I suppose you are right about the alternation error; however the suggest regexp yields: 
    U.S. US-Army
the US-Army has been berry-berry good to me
US-US-Army
US US-Army

    [download]
    Which now does the first case wrong as well.
[reply]
[d/l]

In Section Seekers of Perl Wisdom