c:\@Work\Perl\monks>perl -wMstrict -le
"my $text = '123 abc 456 de 789 fghi 321';
 print qq{A:    '$text'};
 ;;
 do {  printf 'running s/// -> ';
       $text =~ s{ [a-z]+ }{OTHER}xmsg;
       print qq{'$text'};
       }
 while $text =~ m{ [a-z]+ }xms;
 print qq{done: '$text'};
 ;;
 $text = '123 rs 456 tuvw 789 xyz 321';
 print qq{B: '$text'};
 ;;
 $text =~ s{ [a-z]+ }{OTHER}xmsg;
 print qq{   '$text'};
"
A:    '123 abc 456 de 789 fghi 321'
running s/// -> '123 OTHER 456 OTHER 789 OTHER 321'
done: '123 OTHER 456 OTHER 789 OTHER 321'
B: '123 rs 456 tuvw 789 xyz 321'
   '123 OTHER 456 OTHER 789 OTHER 321'