I created a code to sort out these lines of text that would have both search phrases in them. It did it's job without complains. Then I had a need to search lines thusly.Get a line(lineA) > get next line(lineB) > search next line for matches > if matches found print lineA followed by line B

In short I wanted to print line with matches and a line previous to this.

The original code that worked for finding matches in a line was like this (its a bit shortened version here) 

 
open IN, 'sample.fa'|| die("Could not open file!");
open OUT, '>modsample.fa'|| die("Could not open file!");
while ($line = <IN>)
{
if ($line=~m/mamma/&&$line=~m/mia/) {print OUT "$line";}
else {print ".";} #just to look at something while it works 
}

[download]

It found the lines and printed them out. when I modified the script to look for lines and print both matched lines and the one precedening. I got a blank output file. For some reason it could not do its matches. Here is how my modification looks like.

open IN, 'sample.fa'|| die("Could not open file!");
open OUT, '>modsample.fa'|| die("Could not open file!");
while ($line = <IN>)
{$nextline=<IN>;
if ($nextline=~m/mamma/&&$line=~m/mia/) {print OUT "$line$nextline";}
else {print ".";}
}

[download]

Can you explain it to me? And maybe offer some suggestions how to actually accomplish my goal

In reply to What went wrong with this change in code? by naturalsciences

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