regular expression ?!

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

Hi All, I have a question,Initially I thought as a simple one !!! I have a header of a file which is some thing like

SNP    Coor    Alleles    BM19228A    BM19228B    BM19229A    BM19229B
+    BM19231A
[download]

The BM* could be more that 100s.I need to prefix the BMs with a string which is XXXXX_.

Though I could slurp the first header line from the entire file and succeeded in changing the first BM19228A to XXXXX_BM19228A. I am stuch with progressing them with other BMs . Could any one please give suggestions or directions in doing it?
thanks a lot

Comment on regular expression ?! Download Code

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Re: regular expression ?! by moritz (Cardinal) on May 05, 2009 at 12:42 UTC
What have you done so far? Show us the code, maybe it can be easily extended.	[reply]
Re^2: regular expression ?! by Anonymous Monk on May 05, 2009 at 12:48 UTC
`#!/usr/local/bin/perl use strict; use Getopt::Long; use sql_engine; my $string = "XXX2EX_"; #my (@grepnam, @names); while(<>) { chomp; if ($_ =~/SNP/i) { #print $_, "\n"; if ($_ =~s/BM/$string/) { print $_, "\n"; } } }` [download]	[reply] [d/l]
Re^3: regular expression ?! by Anonymous Monk on May 05, 2009 at 12:51 UTC
Sorry its me again. In may actual code it works as `if ($_ =~s/BM*/XXXEX_BM/)`	[reply] [d/l]
Re^4: regular expression ?! by moritz (Cardinal) on May 05, 2009 at 12:52 UTC
Re: regular expression ?! by Utilitarian (Vicar) on May 05, 2009 at 12:54 UTC
have you added the global modifier to the regex? eg. `$firstline=~s/(\s)BM/$1XXXXX_BM/g` [download]	[reply] [d/l]
Re: regular expression ?! by ccn (Vicar) on May 05, 2009 at 12:51 UTC
`perl -ple 's/\bBM/XXXXX_BM/g if $. == 1' file` [download]	[reply] [d/l]
Re: regular expression ?! by AnomalousMonk (Archbishop) on May 05, 2009 at 12:55 UTC
I, too, find it hard to comment on code (you say you can make one substitution successfully) that is not presented. However, one direction for further investigation might be the g regex modifier (see perlre and links therefrom).	[reply]
Re: regular expression ?! by vinoth.ree (Monsignor) on May 05, 2009 at 14:05 UTC
`#!/usr/local/bin/perl use strict; use Getopt::Long; use sql_engine; my $string = "XXX2EX_"; #my (@grepnam, @names); while(<>) { chomp; if ($_ =~/SNP/i) { #print $_, "\n"; if ($_ =~s/BM/$string/) { print $_, "\n"; } } }` [download] In your code this line `if ($_ =~s/BM/$string/)` substitute BM with the literal string XXX2EX_ having it in the variable $string, to prefix XXXXX change the second if condition as `if ($_ =~s/(BM*)/XXXXX_$1/)` Vinoth,G	[reply] [d/l] [select]
Re: regular expression ?! by JavaFan (Canon) on May 05, 2009 at 13:37 UTC
Based on the single line example, I'd write it as: `s/\b(?=BM)/XXXXX_/g;` [download]	[reply] [d/l]