Another good place to look for use of the /x modifier is in perlretut. That said the same functionality as in the above stated regular expression could be written more tersely as: 
/^(?:[\da-f]{2}:){5}[/da-f]{2}$/

[download]
or with /x 
/^(?:
   [/da-f]{2}:
  ){5}
  [/da-f]{2}
 $
/x

[download]
or even shorter if you use qr. 
$x = qr/[\da-f]{2}/;

[download]
(and later on) 
/^(?:$x:){5}$x$/;

[download]

-enlil

In reply to Re: Long regexp un multiple lines by Enlil
in thread Long regexp un multiple lines by Lorand

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