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

Now I have the slowest and the fastest.

#!/usr/bin/perl
use 5.012;
use warnings;
use Benchmark qw(cmpthese);
my @strings = ('a b c', 'ab c d', 'a bcd e f gh', 'abc d');

cmpthese( 0, {
    Eric_Storm  => sub{ for my $string (@strings) { $string =~ s{\b(\w) ((?: \s+ (\w)\b)+)}{$1 . join '', split m|\s+|, $2}gex; } },
    canavanin   => sub{ for my $string (@strings) { $string =~ s/\b(\w)\s+(?=\w\b)/$1/g; } },
    Alan_Moore  => sub{ for my $string (@strings) { $string =~ s/(?<=(? sub{ for my $string (@strings) { $string =~ s/\PL\pL\K (?=\pL(?!\pL))//g; } },
    keep_asc    => sub{ for my $string (@strings) { $string =~ s/[^a-zA-Z][a-zA-Z]\K (?=[a-zA-Z](?![a-zA-Z]))//g; } },
    no_regex    => sub{ for my $string (@strings) { my @s; my $t = ''; 
    for my $el (split /\s+/, $string) {if (length $el > 1) { push @s, $t if $t; $t = ''; push @s, $el; } else { $t .= $el; } }
    push @s, $t if $t;
    #say "@s";
    } },
});

.

           Rate  no_regex Alan_Moore Eric_Storm canavanin  keep_uni keep_asc                                                                                                                                                             
no_regex    98682/s        --       -64%       -65%      -66%      -81%     -87%                                                                                                                                                             
Alan_Moore 274019/s      178%         --        -3%       -6%      -48%     -63%                                                                                                                                                             
Eric_Storm 282855/s      187%         3%         --       -3%      -46%     -62%                                                                                                                                                             
canavanin  291585/s      195%         6%         3%        --      -45%     -60%
keep_uni   528014/s      435%        93%        87%       81%        --     -28%
keep_asc   735254/s      645%       168%       160%      152%       39%       --