Sorry thats wrong, your test data is misleading you :)

you are calculating the numerical range between 2 and 6, which by accident was your input.

now change the input in between:

> echo - 2 - - - 6|perl -lane 'print $F[1]..$F[-1]'
23456
[download]

but a slice works: =)

> echo - 2 - - - 6|perl -lane 'print @F[1..$#F]'
2---6
[download]