Rather than using a complicated regex you could read your records into an array then print in the desired order using an array slice.

use strict;
use warnings;

open my $inFH, q{<}, \ <<EOF or die $!;
#EXTM3U
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=80000
80.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=400000
400.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=700000
700.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1500000
1500.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=2500000
2500.m3u8
EOF

my @records;

push @records, scalar <$inFH>;
push @records, join q{}, map scalar <$inFH>, 1 .. 2
   while not eof $inFH;

print for @records[ 0, 3, 1, 2, 4, 5 ];

[download]

The output.

#EXTM3U
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=700000
700.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=80000
80.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=400000
400.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1500000
1500.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=2500000
2500.m3u8

[download]

I hope this is helpful.

Cheers,

JohnGG

In reply to Re: Multiline regex for moving lines? by johngg
in thread Multiline regex for moving lines? by bowei_99

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