Removing spaces between single letters

Question

I have a string that may contain an arbitrary number of single-letters separated by spaces. I am looking for a regex (in Perl) that will remove spaces between all (unknown n

Answer 1

This should do the trick:

my $str = ...;

$str =~ s/ \b(\w) \s+ (\w)\b /$1$2/gx;

That removes the space between all single nonspace characters. Feel free to replace \S with a more restrictive character class if needed. There also may be some edge cases related to punctuation characters that you need to deal with, but I can't guess that from the info you have provided.

As Ether helpfully points out, this fails on one case. Here is a version that should work (though not quite as clean as the first):

s/ \b(\w) ( (?:\s+ \w\b)+ ) /$1 . join '', split m|\s+|, $2/gex;

I liked Ether's test based approach (imitation is the sincerest form of flattery and all):

use warnings;
use strict;
use Test::Magic tests => 4;

sub clean {
    (my $x = shift) =~ s{\b(\w) ((?: \s+ (\w)\b)+)}
                        {$1 . join '', split m|\s+|, $2}gex;
    $x
}

test 'space removal',
  is clean('ab c d')       eq 'ab cd',
  is clean('a bcd e f gh') eq 'a bcd ef gh',
  is clean('a b c')        eq 'abc',
  is clean('abc d')        eq 'abc d';

returns:

1..4
ok 1 - space removal 1
ok 2 - space removal 2
ok 3 - space removal 3
ok 4 - space removal 4