Looks like fixed width columns, so use that fact...

while( <DATA> ) {
    my $ieu = substr( $_, 34, 7);
    $ieu =~ s/\s+//g;
    substr( $_, 34, 7) = sprintf("%-7s", $ieu || '-');
    print;
}
__DATA__
0601 3      NORM 2  ALLO XLF753         U 0045 0050
0603 5      NORM 2  ALLO ADR2CG           0430 0438
0604 6      NORM 2  ALLO AF681VC  i     U 0500 0510
0605 7      NORM 2  ALLO AF651PQ  i       0515 0523
0606 8      NORM 2  ALLO AF713BR  i       0445 0453
0607 9      NORM 2  ALLO AFR100M  i       0520 0533
0609 11     NORM 2  ALLO GJT775   i E     2300 2315
0610 12     NORM 2  ALLO AF661WN  i       0450 0500 0500

[download]

Output:

0601 3      NORM 2  ALLO XLF753   U       0045 0050
0603 5      NORM 2  ALLO ADR2CG   -       0430 0438
0604 6      NORM 2  ALLO AF681VC  iU      0500 0510
0605 7      NORM 2  ALLO AF651PQ  i       0515 0523
0606 8      NORM 2  ALLO AF713BR  i       0445 0453
0607 9      NORM 2  ALLO AFR100M  i       0520 0533
0609 11     NORM 2  ALLO GJT775   iE      2300 2315
0610 12     NORM 2  ALLO AF661WN  i       0450 0500 0500

[download]

I've added $ieu || '-' so that an empty column is replaced with a dash. You may not want that, but I find dealing with delimetered columns easier than fixed width.

update: added output

In reply to Re: gathering of some elements of a list by FunkyMonk
in thread gathering of some elements of a list by steph_bow

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