Re: Replacing exactly the found instance in REGEX


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Re: Replacing exactly the found instance in REGEX

by sathiya.sw (Monk)

on Dec 09, 2008 at 12:09 UTC ( [id://729140]=note: print w/replies, xml )

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in reply to Replacing exactly the found instance in REGEX

A simple change in your code would achieve this,

$string = "useridagohiluserid>traderidagohiltraderidjiagohilji";
if ($string =~ /traderid(.*?)traderid/sig)
{
   $string =~ s/(?<=traderid)$1(?!=traderid)/myword/ ;
}
print "$string\n" ;
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Change which am asking you to do is simple, is called as lookarounds in regex.

(?<=TEXT) --> mean look behind.
(?!=TEXT) --> mean look ahead.
So you wanted traderid to be presented in both the side, by confirming that again in the substitution you can achieve it.

Sathiya

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Re^2: Replacing exactly the found instance in REGEX
by johngg (Canon) on Dec 09, 2008 at 12:52 UTC

You have made a slight mistake with your look-ahead syntax.

`(?=pattern)`	Positive look-ahead	match is followed by pattern
`(?!pattern)`	Negative look-ahead	match is not followed by pattern
`(?<=pattern)`	Positive look-behind	match is preceeded by pattern
`(?<!pattern)`	Negative look-behind	match is not preceeded by pattern