#!/usr/bin/perl
use strict;
use warnings;

my $in = "foo bar blivitz done";

$in =~ s/\s+/\n/g;      # replace spaces with \n

print "after first regex: $in \n";

# $in =~ s/[a-zA-Z]\n[a-zA-Z]/$1\ $2/g;
$in =~ s/([a-zA-Z])\n([a-zA-Z])/$1 $2/g;  # remove newlines, restore spaces

print "after second regex: $in \n";


=head execution:

ww@GIG:~/pl_test$ perl 675941.pl
after first regex: foo
bar
blivitz
done
after second regex: foo bar blivitz done
ww@GIG:~/pl_test$


=cut