StringReplace, String, clipboard, :, ©
StringSplit, word_array, String, ©
MsgBox, ACC = %word_array1% PASS = %word_array2%

Source:=Clipboard
Found:=RegExMatch(Source, "U)(?:\s|\R|^)хххххх:\s+(.+)(?:\s|\R|$)", Match)
If Found
  MsgBox, %Match1%
Else
  MsgBox, Не найдено.

; MyAccount:MyPassword

; 1.
intPos := InStr(Clipboard, ":")

IfEqual, intPos, 0
    MsgBox, , Method 1, Clipboard data:`n`r%Clipboard%`n`rnot contain [Account:Password] form.
Else
{
    strAccount  := SubStr(Clipboard, 1, intPos - 1)
    strPassword := SubStr(Clipboard, intPos + 1)
    MsgBox, , Method 1, Account: %strAccount%`n`rPassword: %strPassword%
}


; 2.  - не проверяем форму
Loop, Parse, Clipboard, :
{
    MsgBox, , Method 2, %A_LoopField%
}


; 3.
intPos := RegExMatch(Clipboard, "^(.*?):(.*)$", strSubMatch)

IfEqual, intPos, 0
    MsgBox, , Method 3, Clipboard data:`n`r%Clipboard%`n`rnot contain [Account:Password] form.
Else
{
    strAccount  := strSubMatch1
    strPassword := strSubMatch2
    MsgBox, , Method 3, Account: %strAccount%`n`rPassword: %strPassword%
}

f4::
send, ^{vk43}
Source=%clipboard%
ACC=^[^:]+
PASS=[^:]+$
RegExMatch(Source, ACC, Found)
RegExMatch(Source, PASS, Found1)
return
f5::
send, %Found%
return
f6::
send, %Found1%
return