Thanks a lot Miller for your reply. However, it does not seem to work

Here is my start file :

141    
142    
143    REGULATION SLOT LAYOUT + REGULATED FLIGHTS
144
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I have tried to replace the text by the number (here 143) and it works

But it seems that the number at which step the text "REGULATION SLOT LAYOUT + REGULATED FLIGHTS" is likely to change.

Where did I go wrong ?
Here is my code

my $file = "$ARGV[0]";

################# END OF THE DECLARATION OF THE ARGUMENTS

my $Current_Dir = `pwd`;
# print STDOUT "the current directory is $Current_Dir";

# open the ALL_FT file 
open(INFILE,"$ARGV[0]") or die "Can't open $ARGV[0]: $!";

# name of the OUTFILE
# do not forget the "" if 
# never put a \n at the end of the OUTFILE name otherwise it does not 
+create the output
 my ${outfile_name} = "bon_format_$file";


# to open the file
# OUTFILE is the name of the HANDLE in this case
  open (OUTFILE, ">${outfile_name}.csv") or die "Can't open ${outfile_
+name}.csv: $!";

my @Parts;
my $part;

while (<INFILE>) {
        if (/^143/..eof(INFILE)){
    # the lines are composed of elements separated by a point comma
        my $Line = $_;
            my @Elements = split(";", $Line);
        my $element = $Elements[1];
        @Parts = split(" ",$element);
         
            foreach $part(@Parts){
            print OUTFILE ";$part";        
            }
            print OUTFILE "\n";
        }
    }
close INFILE;
close OUTFILE;
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