need help to replace string in a line

vkp has asked for the wisdom of the Perl Monks concerning the following question:

hi there, i need to replace some string in a line. The string could be (for example) nf=6 or nfabc = 7 or nf = {(3)*(3)} or nfabc = {(1)*(1)}. I am using following

$_=~/ +nf.*? *\=? *\d+/

for nf =4 or nfabc=4. and second is

$_=~/ +nf.*? *\= *.*?\}/

for nf or nfabc ={} like stuff. The second is working fine. But the first is also targeting the {} stuff and it is taking pattern like nf={4} g=4 matched, and returning $& as nf={4} g=4. I know it is because of \d+ in last. But i want to make first line only to match nf=4 or nfabc=4. Not to {} stuff, because it means different for me. Please modify first code line so that i can get correct match. thanks.

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Re: need help to replace string in a line by moritz (Cardinal) on Nov 24, 2012 at 16:22 UTC
I haven't checked it, but I guess your extensive use of `.?` is causing trouble. That can match lots of stuff you don't want it to match. Be more specific! For example: `/ nf\w \h* = \h* \d+ /x # ^ don't make the = optional # ^^^ not arbitrary characters, just allow word characters / nf\w+ \h* = \h* \{ [^}]+ \}/ # ^^^^ don't allow a closing bracket inside the bra +ckets` [download] Perl 6 - the future is here, just unevenly distributed	[reply] [d/l] [select]

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Re: need help to replace string in a line
by moritz (Cardinal) on Nov 24, 2012 at 16:22 UTC

I haven't checked it, but I guess your extensive use of .*? is causing trouble. That can match lots of stuff you don't want it to match. Be more specific!

For example:

/ nf\w* \h* = \h* \d+ /x
#           ^ don't make the = optional
#   ^^^ not arbitrary characters, just allow word characters

/ nf\w+ \h* = \h* \{ [^}]+ \}/
#                    ^^^^ don't allow a closing bracket inside the bra
+ckets
[download]

Perl 6 - the future is here, just unevenly distributed

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