Problem with rename in a loop

[Alberto Lopez]

Hello I am trying to rename some variables within a loop, but it returns me error.
I have some variables like F10_sadk_ifs_t10y_ed4_qe_90 and I want them as F10_sadk-ifs_t10y_ed4_qe_90.
I tried this:

   foreach a in F10 F15 {
   foreach b in sapk sadk {
   foreach c in t3m t6m t1y t2y t3y t5y t7y t10y {
   foreach f in mp1 mp2 mp3 mp4 ff1 ff2 ff3 ff4 ed1 ed2 ed3 ed4 {
   foreach s in qe nqe
   foreach t in 68 90
  
 rename `a'_`b'_ifs_`c'_`f'_`s'_`t' `a'_`b'-ifs_`c'_`f'_`s'_`t'
 }
 }
 }
 }

[Jorrit Gosens]

Var names cant have dash. Use underscore.

Edit:
I do now see that this would negate the renaming loop altogether. So maybe just leave as is?
See section 11.3 here: https://www.stata.com/manuals13/u11.pdf for naming rules

    foreach a in F10 F15 {
   foreach b in sapk sadk {
   foreach c in t3m t6m t1y t2y t3y t5y t7y t10y {
   foreach f in mp1 mp2 mp3 mp4 ff1 ff2 ff3 ff4 ed1 ed2 ed3 ed4 {
   foreach s in qe nqe {
   foreach t in 68 90 {
  
 rename `a'_`b'_ifs_`c'_`f'_`s'_`t' `a'_`b'_ifs_`c'_`f'_`s'_`t'
 }
 }
 }
 }
 }
 }