Присоединяйтесь к двум файлам на основе общего поля

Если у вас есть GNU tools:

find -maxdepth 1 -type f -printf '%s %p\0' | 
  awk -v RS='\0' '{a[$0]=$1;s+=$1;}
                  END{m=s/NR; for(i in a){if(a[i]>=m){print i}}}' 

А если нет:

perl -le 'opendir(D,"."); @F=readdir(D); @files=grep{-f $_}@F; 
    for (@files){$s= -s $_; $t+=$s; $f{$_}=$s} 
    print join "\n",grep{$f{$_}>=$t/scalar(@files)}@files' 

Что можно расширить до:

#!/usr/bin/perl 

## Open the current directory as D
opendir(D,".");
## Read the contents of D into @F
@F=readdir(D);
## Collect only the files, no dirs etc. 
@files=grep{-f $_}@F;
## For each file, as $_
for (@files){
    ## Get the size
    $s= -s $_;
    ## Add the size to the total
    $t+=$s;
    ## Save the size in the hash %f whose keys are the file names
    $f{$_}=$s
}
## Get all files whose size is greater than the average
my @wanted=grep{$f{$_}>=$t/scalar(@files)}@files;
## Print the elements of the array @wanted with a newline after each of them
print join "\n", @wanted ;
print "\n";