Isnt it enough that it has it in the shebang line as well '#!/usr/bin/perl' ?

What's "it"?, the "#!"? No. When I said it has to be the very first thing in the file, I meant it has to be the very first thing in the file.

$ od -c a.pl
0000000 357 273 277   #   !   /   u   s   r   /   b   i   n   /   p   
+e
0000020   r   l  \n   p   r   i   n   t   (   "   H   e   l   l   o
0000040   W   o   r   l   d   \   n   "   )   ;  \n  \n
0000054

$ a.pl
-bash: ./a.pl: cannot execute binary file

$ perl -i.bak -ple"s/^\xEF\xBB\xBF// if $.==1" a.pl

$ od -c a.pl
0000000   #   !   /   u   s   r   /   b   i   n   /   p   e   r   l  \
+n
0000020   p   r   i   n   t   (   "   H   e   l   l   o       W   o   
+r
0000040   l   d   \   n   "   )   ;  \n  \n
0000051

$ perl a.pl
Hello World
[download]

i tried clciking the link with BOM but it wont load

It's the Wikipedia page on "byte-order mark". I don't see why you couldn't load it.

When a script source is considered to be utf-8?

Either it is or it isn't. There's no "considered" about it. If you saved it using UTF-8 as the encoding, it's UTF-8. If you used another encoding, it isnt.

But yes, I meant when the source is UTF-8.

Perl will assume the source is encoded using iso-8859-1 unless use utf8; is used.

Thanks i can see the 1st 3 bytes if BOM is used. Still the link is disfunctional and i dont know why BOM is used.

i try using

#!
#!/usr/bin/perl -w
[download]

and

#!/usr/bin/perl -w
use utf8;
[download]

and save my script with the use of Notepad++ with utf8 encoding, but when i upload it wont run. why?

Also in my scripts aprt from the perl syntax i use greek characatets. does that mean that i have to save my scripts in utf8 encoding or ansi? What iam trying to say here is based on what criteria should i choose as to what encoding i must pick for saving my perl scripts? Why ut8? why utf8 without Bom? why ansi? is there a reason? Why locally all encodings work and remotely only ansi does?

save my script with the use of Notepad++ with utf8 encoding, but when i upload it wont run. why?

Already answered

[ Oops, posted too soon by accident, so I'll post the rest here ]

Still the link is disfunctional

No. Like i already said, your end is what's dysfunctional. There's a whole web out there to google, so no excuse.

Also in my scripts aprt from the perl syntax i use greek characatets. does that mean that i have to save my scripts in utf8 encoding or ansi?

ANSI is not a specific encoding. It's Windows terminology to use the local encoding, for some definition of local.

But it's moot. Unless you use the broken/weird use encoding, Perl only understands iso-8859-1 (use utf8; off) and UTF-8 (use utf8; on).

iso-8859-1 doesn't support greek characters, so that leaves UTF-8.

why utf8 without Bom?

U+FEFF is only a BOM if it's the very first character of a file. (It's a zero-width no-break space elsewhere.)

#! is only a shebang if it's the very first characters of a file.

That means you can only use one or the other.