use strict;
use warnings;

my $element = q{coucou};
my $inFile  = q{EXEMPLE.txt};
my $outFile = qq{RESEARCHED_text_${element}.txt};

open my $inFH, q{<}, $inFile
   or die qq{open: $inFile: $!\n};
open my $outFH, q{>}, $ourFile
   or die qq{open: $outFile: $!\n};

while ( <$inFH> )
{
    next unless m{(.*?)$element(.*);
    print $outFH;
    my $beforeElement = $1;
    my $afterElement  = $2;
    # Do something here with your captured text ...
}

close $inFH
   or die qq{close: $inFile: $!\n};
close $outFH
   or die qq{close: $outFile: $!\n};