sub process_file {
    my $dir_configs=$_[0];
    ##optimisation using -d -l -f -s just once for return and also for adding

    #if current "file"(unix terminology) is a directory and the yaml configuration
    #tells us to eliminate directories from the search we do so by returning from the
    #callback
    return if -d $File::Find::name && ! $dir_configs->{dir};

You call stat on the file.

    return if -l $File::Find::name && ! $dir_configs->{link};

You call lstat on the same file.

    return if -f $File::Find::name && ! $dir_configs->{file};

You call stat on the same file again.

    return if -s $File::Find::name < $config->{minsize};

You call stat on the same file again.

    unless($File::Find::name =~  /$dir_configs->{regex}/) {
        if(-d $File::Find::name) {

You call stat on the same file again.

            $File::Find::prune=1;
        }
        return;
    }

    my ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
        $atime,$mtime,$ctime,$blksize,$blocks)
    = stat($File::Find::name);

You call stat on the same file again. You declare 13 variables but you are only using one.

    my $last_modif_time=DateTime->from_epoch(epoch=>$mtime);
#    printf "%s %s %s %s\n",
#    $File::Find::name,
#    file2sha1($File::Find::name),
#    -s $File::Find::name,

Commented out but if not you call stat on the same file again.

#    $last_modif_time;

    add_to_db(file2sha1($File::Find::name),$last_modif_time,-s $File::Find::name,$File::Find::name);

You call stat on the same file again. You call add_to_db() which calls stat or lstat three more times.

    #print Dumper $dir_configs;
};

In total you call stat or lstat ten times on the same file (eleven times if you uncomment the printf statement.) You also use $File::Find::name in most places where $_ would have the same effect.

sub process_file {
    my $dir_configs = $_[ 0 ];
    ##optimisation using -d -l -f -s just once for return and also for
+ adding

    #if current "file"(unix terminology) is a directory and the yaml c
+onfiguration
    #tells us to eliminate directories from the search we do so by ret
+urning from the
    #callback
    return if -l && ! $dir_configs->{ link }; # call lstat on current 
+file to test for symlink

    my ( $size, $mtime ) = ( stat )[ 7, 9 ];

    return if -d _ && ! $dir_configs->{ dir };
    return if -f _ && ! $dir_configs->{ file };
    return if $size < $config->{ minsize };
    unless ( $File::Find::name =~ /$dir_configs->{regex}/ ) {
        if ( -d _ ) {
            $File::Find::prune = 1;
        }
        return;
    }


    my $last_modif_time = DateTime->from_epoch( epoch => $mtime );
#    print "$File::Find::name ", file2sha1( $_ ), " $size $last_modif_
+time\n",

    add_to_db( file2sha1( $_ ), $last_modif_time, $size, $File::Find::
+name );
    #print Dumper $dir_configs;
}
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