use strict;
use warnings;

my $previous_x = 0;

while (<DATA>) {
    my ($x, $y) = split;
    next if $x < $previous_x;
    $previous_x = $x;
    print;
}

__DATA__
0.0036759    0.4018006
0.0036962    0.4074616
0.0037064    0.4124646
[rest of input data omitted for brevity]