$want = 'This is a real number, 493,826.26268';
($have = (($orig) =~ s{ \d+\.?\d* }{ $& * 4 }erx )) =~ s{ \d+ }{
    $& =~ s/ (?<=\d) (?= (?:\d{3} )+ (?!\d) ) /,/xrg; }ex;
$intpart = $&;
is $intpart, 493826, '$& int part captured';
is $have, $want, 'Insert commas where appropriate';