use Modern::Perl '2014';
use Number::Interval;
use List::Util qw/first/;

# FILE1 data emulation
my @FILE1 = qw/99269 550 100 126477 1700/;

my @interval_objects;
while (<DATA>) {
    chomp;
    my ($start, $end, undef) = split;
    push @interval_objects,
        Number::Interval->new(
            IncMax => 0,
            IncMin => 0,
            Min    => $start,
            Max    => $end,
        );
}

for my $datapoint (@FILE1) {
    my $found = first {$_->contains($datapoint)} @interval_objects;
    say "$datapoint is in $found" if $found;
}

# FILE2 data emulation
__DATA__
517 1878 forward
700 2500 forward
2156 3289 forward
99000 100000 forward
22000 23000 backward