Have a look at this: 
use strict;
use Data::Dump qw/dump/;

my %data;

while (<DATA>) {
    chomp;
    my ( $field1, $field2, $field3, $field4 ) = split '\s+';
    $data{$field1}{$field2}{'min'} = $field3
        if ( not defined $data{$field1}{$field2}{'min'}
        or $field3 < $data{$field1}{$field2}{'min'} );
    $data{$field1}{$field2}{'max'} = $field4
        if ( not defined $data{$field1}{$field2}{'max'}
        or $field4 > $data{$field1}{$field2}{'max'} );
} ## end while (<DATA>)
print dump( \%data );

__DATA__
253868    20    317    2628
253868    20    317    7294
256158    9    329    371
256158    9    329    86450
728481    1    353    1361
154664    7    440    449688
154664    7    440    563

[download]
Output: 
{
  154664 => {  7 => { max => 449688, min => 440 } },
  253868 => { 20 => { max =>   7294, min => 317 } },
  256158 => {  9 => { max =>  86450, min => 329 } },
  728481 => {  1 => { max =>   1361, min => 353 } },
}

[download]
Getting the data-structure into your output format is left as exercise for the reader.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

In reply to Re: Minimum and Max values from same Key by CountZero
in thread Minimum and Max values from same Key by cowboyrocks

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